Safety control device for electrically operated machines



J. o. KLEBER 2,418,356

April 1, 1947.

SAFETY CONTROL DEVICE FOR ELECTRICALLY OPERATED MACHINES 2 SheetsSheet 1Filed July 1, 1944 INVENTOR.

3 Je/rsa/vahzrsffi J. o. KLEBER 2,418,356 SAFETY CONTROL DEVICE FORELEGTRICALLY OPERATED MACHINES April 1, 1947.

2 Sheets-Sheet 2 Filed July 1, 1944 JNVENTOR. fie/(soxv 0. f'fLEBBPPatented Apr. 1, 1947 SAFETY CONTROL DEVICE FOR ELECTRI- CALLY OPERATEDMACHINES Jackson 0. Kleber, Long Island City, NY.

Application July 1, 1944, Serial No. 543,127

3 Claims.

This invention relates to a safety control device for electric sewingmachines.

The primary object of the invention is to provide a safety deviceadapted to protect the fingers of sightless persons or others whenoperating elec tric. sewing machines.

It is also an object of the invention to bring the sewing machine to acomplete and sudden stop whenever the fingers of an operator comedangerously close to the needle.

In accordance with the invention, a beam of light is directed downtowards the region in front of the sewing machine needle and this lightis reflected upwardly onto a photoelectric cell. The photoelectric cellis connected with suitable control equipment for immediately stopp ngthe sewing machine responsive to interruptions of the reflected light,as when an operators finger enters the region dangerously close to theneedle.

While I am aware that photoelectric cell equipment has heretofore beenused for the control of various types of machines. the use of suchequipment for insuring the safety of the operators of the sewingmachines involves a number of special problems Which so far as I amaware, have not been heretofore encountered or solved. It should firstbe noted that for the automatic stopping of a sewing machine, theequipment must be so arranged that the operator may normally bring hisfingers up to the presser foot and be able to feed the cloth, or othermaterial to be sewed. along beneath the pressor foot without causing themachine to be automatically stopped. That is, the operator should befree to move his hands and fingers up to the presser foot, and alsoaround the sides and to the rear thereof to properly guide the workwithout stopping the machine. Also, of course, the work should be freeto travel through its normal p th under and around the presser footwithout being liable to interrupt the light and automatically stoppingthe machine. However, the instant that the operator brings his fingersaccidentally over the area of the upper surface of the presser foot,then to be effective, the automatic equipment must stop the machine atonce and before there is 010-,

portunity for the needle to take even one additional downward stroke.

The immediate stopping of an electric sewing machine involves not onlythe difficulty of overcoming the inertia of the rapidly moving mechanismin the sewing machine itself, but also the substantial inertia of therapidly rotating drive motor must also be taken into consideration.

In accordance with the present invention, the

above noted diliiculties have been overcome by directing the beam oflight downwardly, preferably at a sharp angle from the side, onto thepresser foot which is formed or provided with a reflective surface insuch a position that the beam is reflected upwardly, preferably at asharp angle onto the photoelectric cell.

With the original light beam and the reflected beam located in thesepositions, the above described normal manipulations of the work and ofthe operators hands and fingers, may be carried out without interruptingthe light beam. However, immediately upon the operator's fingers movinginto a position over the presser foot in front of the needle, thereflected light is interrupted for actuating the stop mechanism.

In order to have the stop mechanism operate substantiallyinstantaneously and positively, the photoelectric cell is preferablyconnected with an improved amplifier and circuit arrangement forimmediately and positively operating a relay the moment the light beamis interrupted. This relay in turn, is preferably arranged to control aquick acting solenoid brake which acts to at once stop the sewingmachine per se. At the same time, the relay is preferably connected toactuate a quick acting solenoid controlled clutch for disconnecting themotor so that its inertia will not tend to cause the machine to furthermove the sewing needle.

These and other objects and features of the invent on and the means fortheir attainment will be clearly apparent from the following detaileddescription, taken in connection with the accompanying drawingsillustrating one embodiment by which the invention may be realized andin which:

Fig. 1 is a view in front elevation showing a sewing machine in whichthe improvements of this invention have been incorporated;

Fig. 2 is a view, in plan, showing the presser foot;

Fig. 3 is a detail view showing the sectional clutch rod and the devicesenabling the sections to be automatically released;

Fig. 4 is a transverse sectional view taken in the plane indicated bythe line 4-4 of Fig. 3 and looking in the direction of the arrows;

Fig. 5 is a vertical sectional view taken in the plane indicated by theline 55 of Fig. 1, looking in the direction of thearrows and showing thebrake means to halt the sewing machine; and

Fig. 6 shows the circuit diagram by which the electrically actuateddevices of this invention are controlled,

Referring first to Fig. 1, there is there shown a conventional sewingmachine indicated as a whole at If), having the reciprocating needle l2and presser foot l4. An. upper surface l5 of the presser foot M, Fig. 2,is polished or otherwise provided with a surface that reflects lightrays. On the end of the sewing machine proximate the needle I2 is atubular casing l6 containing a light source and so disposed that lightfrom the light source l1, Fig. 6, is directed to and through a lens l8onto the upper reflecting surface [5 of the presser foot l4, and fromsuch mirrored upper surface l5 it is directed to fall on a photoelectriccell 20 in a casing 2| carried on the sewing machine on the oppositeside of the needle I2 from the source of light l1.

The operating shaft 22, Figs. 1 and 5, extending outwardly through theright hand side, as viewed, of the sewing machine, is provided with abrake drum 24 about which a strap 25 extends to a solenoid 28, whereby,when the solenoid is energized, the brake strap is drawn upwardly andbinds on the drum and serves to promptly stop rotation of the brake drumand thereby the rotation of the shaft 22, which in turn results inimmediate cessation of the needle movement.

Also carried on the shaft 22 is a pulley 32 which is driven by means ofbelt 38. from a driving pulley 34 rotated by the motor 40 carriedbeneath the bed 36 of the machine. Extending from the motor 40 is acontrol rod comprising an upper section 42 and a lower section 44, whichis provided with a hook 46 at its lower end for connection with an arm48 on the pivoted foot treadle-50. The upper end of the rod 42, 44 isconnected with a clutch in the casing 52 on the motor. Pressure on thefoot treadle 50 clutches the motor 40 to the sewing machine drivethrough the control rod 42, 44 and simultaneously releases the brake 26acting on the machine in a manner hereinafter described in connectionwith the electrical circuits operating this instrumentality. 1

, As shown in Figs. 1 and 3, the control rod 42, 44 is provided with ahook member 46, 54 at its lower end whereby the rod is removablyconnected with an arm 48 on the foot treadle 50, and the upper section42 is connected with the clutch 52 of the motor. 5

It is contemplated in accordance with this invention, for purposes ofsafety, that pressure on the foot treadle 50 will clutch the motor 40 tothe machine. On the other hand, when pressure on the treadle isreleased, or what is equivalent thereto, should the rod break or itssections 42, 44 separate, the motor is disconnected and the brakeapplied to the machine. To this end, the lower section 44 is formed witha plurality of upwardly facing teeth 56 and the upper end of section 44enters a frame 58 on a solenoid bracket 69 carrying instrumentalities bywhich the rod section 42 and the rod section 44 are connected to move as,a unit. Asshown (Fig. 4)., the rear wall Bllof the bracket is providedat one extremity, the left (as viewed), with side wall (34, and havingintegral therewith a front wall 66. On the front wall section 66 ispivotally mounted a pawl 68, thetooth of which is adapted to enter oneof the spaces between the teeth 56 to retain the lower rod section 44within the frame 58.- At

its upper end, the connecting plate is shown as formed with a socket 12in which the lower end of the upper rod section 42 extends and is heldby a set screw 14. The upper rod section is connected to the clutch 52by the arm 53 and is 4 normally urged in an upward direction by spring55. Mounted on the front face, as viewed, of the bracket 60 is asolenoid 16, the core 18 of which, upon energization of the solenoid, ismoved to trip the detent 68 and rock the detent out of engagement withthe teeth on the lower control rod 44 thereby disconnecting the rodsections.

Pressure of the foot on the foot treadle draws the rod 42, 44 downwardlythereby actuating the clutch to thereby connect the motor 40 with thedriving shaft of pulley 34, to operate the sewing machine. Conversely,relieving the foot pressure disengages the clutch. Similarly,disconnection of the control rod sections interrupts the downward pullon the clutch and thereby also releases the clutch.

Referring now to Fig. 6 wherein are shown the various elements of theelectrical circuits and other electrically actuated devices controllingthe apparatus hereinbefore described, light source H is of a variableintensity (in this case it is merely lit by an alternating current).Other methods of varying its intensity such as a rotating shutter orvibrating reed might be used.

The light from light source ll is focused by lens l8 to fall upon thereflecting surface l5 and then be reflected to the photoelectric cell20. The output of this photoelectric cell is then amplified by amplifier32 and hence appears on the primary side of transformer 14 as directcurrent impulses. (This same condition will be true regardless of howthe light intensity of light source I1 is varied.) In passing throughtransformer 14, these direct current impulses are again changed toalternating current through the action of the transformer 14.

Rectifier 84 then changes this alternating current back to directcurrent which is used to control relay 85. The operation is as follows:

As long as a varying light falls on the photoelectric cell 20, a varyingor impulse direct current appears on the primary of transformer 14 andan alternating current appears on the secondary of transformer 14. Thiscurrent is then rectified to v direct current by rectifier 84 and holdsrelay 86 in operation as shown in Fig. 6. V

The instant the light falling on photoelectric cell 20 is interrupted,the current'in the primary of transformer 14 becomes steady (the steadydirect current of the output stage of amplifier 82). As a result of thisno voltage appears on the secondary of transformer 74 and relay 86becomes de-energized, thus closing its contacts (normally held open) andcauses the treadle to effect disconnection of the rod by electromagnet16 and brake solenoid 28 to function and to instantaneously stop themachine.

A novel feature of this operation, unlike other photoelectric devices,is that the current in relay 86 goes from maximum (while the light isuninterrupted) to zero (when light is interrupted), and this results inrapid operation of relay 86.

In other photoelectric control circuits, the current in the controlrelay 86 would decrease from a higher to a lower. level rather than froma higher to zero level as in this invention.

Various modifications will occur to those skilled in the art in thedisposition and configuration of the component elements going to make upthe invention as a whole as well as in its entirety, and no limitationis intended by the phraseology of the foregoing description orillustrations in the the appended claims.

What is claimed is:

1. Safety apparatus for immediately stopping electrically driven sewingmachines when the operators fingers approach the needle, said apparatusbeing adapted for machines of the type having a vertically reciprocatingneedle and accompanying presser foot beneath which the work is fed, saidapparatus comprising means for directing a beam of light downwardly ontothe upper surface of the presser foot in front of the needle and in aposition for reflection at a relatively sharp angle from said surfaceupwardly, a photoelectric cell positions substantially above the presserfoot to receive the reflected beam, an electromagneticaliy operatedbrake for stopping the main shaft of the machine, an electromagneticallyoperated clutch for disconnecting the drive motor, and electric circuitand relay means operative under the control of said photoelectric cellto immediately operate said brake and clutch responsive to obstructionof said reflected light beam. 4

2. Safety apparatus for immediately stopping electrically driven sewingmachines when the operators fingers approach the needle, said apparatusbeing adapted for machines of the type having a vertically reciprocatingneedle and accompanying presser foot beneath which the work is fed, saidapparatus comprising means for directing a beam of light downwardly fromone side onto a surface area on the upper side of the presser foot infront of the needle and in a position for reflection at a relativelysharp angle from said surface upwardly at the other side of the presserfoot, a photoelectric cell positioned substantially above the presserfoot to receive the reflected beam, an electromagnetically operatedbrake for stopping the machine, an electric circuit means operativeunder the control of said photoelectric cell to immediately operate saidbrake responsive to obstruction of said reflected light beam.

3. Safety apparatus for immediately stopping electrically driven sewingmachines when the operators fingers approach the needle, said apparatusbeing adapted for machines of the type having a vertically reciprocatingneedle and accompanying pressor foot beneath which the work is fed, saidapparatus comprising means for directing a beam of light downwardly ontothe upper surface of the presser foot in front of the needle and in aposition for reflection from said surface upwardly, a photoelectric cellpositioned to receive the reflected beam, and electromagneticallyoperated means for stopping the machine, and electric circuit meansoperative under the control of said photoelectric cell to immediatelyoperate said stopping means responsive to obstruction of said reflectedlight beam.

JACKSON 0. KLEBER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

